1. Field of the Invention
The present invention relates to the repetitive generation of electronic signals, and more particularly to electronic signal oscillators having close tolerance, and highly precise signals in the very high frequency range measured in megacycles.
2. Description of the Prior Art
Frequency signal oscillators that generate electronic signals repetitively at consistent speeds or frequencies have a wide range of uses in electronic and electrical equipment. Testing equipment especially used for testing the responses of circuits in electronic and electrical equipment often require a frequency generator or oscillator. Preferably, the oscillator should cover a wide range of frequencies to test the electronic circuit equipment thoroughly.
In the past, such oscillators have been provided by multivibrators. Calibration of the frequency to be used in a test was accomplished by varying resistors or capacitors in the multivibrator oscillator. However testing of some of the very high speed electronic equipment presently available requires precise, stable readily controllable oscillator frequencies in the range of 10 to 1 megahertz (MHz) (i.e. cycle periods on the order of 100 to 1000 nanoseconds (ns)).
Conventional multivibrator oscillators, however, when tuned to a particular frequency, must be re-tuned or recalibrated for generation of signals at different frequencies.
Moreover the electrical tuning controls for such conventional oscillators have to be positioned at or very near the oscillators to minimize sensitive long leads which would otherwise pick up and convey excessive noise to the circuit, resulting in an unstable condition in the oscillator. In addition, multivibrator jitter on the order of nanoseconds between pulses, while acceptable in oscillators in the millisecond frequency range, made use of such multivibrator oscillators unreliable in the nanosecond range of frequencies.
It has been sought for some time to have and to use a very high speed frequency generator or signal oscillator capable of providing signals in the 100 to 1,000 nanosecond range having a stability of .+-.2 nanoseconds or better. Further, it is desired to have such a high speed, reliable oscillator capable of having its frequency selectively changed during oscillation, in reasonably fine increments on the order of 5 nanoseconds, through manual controls (which may be remotely positioned) which electronically select the frequency within the oscillator circuit. It is sought, further, to provide such a reliable, manually selectable electronically programmable oscillator with a direct digital readout.